Most home appliances have infrared interfaces, and through IR learning, control instructions of various home appliances may be copied conveniently. The principle of IR learning is to record the waveform widths of the transmitting infrared signals. This method may replay infrared signals in any coding form. However, since an infrared signal has a relatively long waveform, and the size of the data may be rather large, thus creating problems in the transmission and storage of the learned data.
Currently, a common infrared signal utilizes the Pulse Width Modulation (PWM) encoding technique to generate waveform data, i.e. PWM data. The signals propagated by the PWM in lower layers are digital signals, expressed in a waveform of 0/1. Theoretically, through the PWM, data is transmitted by means of combinations of a limited amount of waveforms each with a certain length in the lowermost layer.